688 research outputs found
COSMOS 2044: Lung morphology study, experiment K-7-28
Researchers examined the effect of microgravity during spaceflight on lung tissue. The ultrastructure of the left lungs of 5 Czechoslovakian Wister rats flown on the 13 day, 19+ hour Cosmos 2044 mission was examined and compared to 5 vivarium and 5 synchronous controls at 1-g conditions, and 5 rats exposed to 14 days of tail suspension. Pulmonary hemorrage and alveolar adema of unknown origin occurred to a greater extent in the flight, tail-suspended, and synchronous control animals, and in the dorsal regions of the lung when compared with the vivarium controls. The cause of these changes, which are possibly due to an increase in pulmonary vascular pressure, requires further investigation
Techno-economic WEC system optimisation ā Methodology applied to Wavebob system definition
The overall system optimisation of wave energy
converters remains a challenging task. Firstly, this
is associated with the large number of system
parameters and their related constraints, secondly,
the complexity of numerical system representations
capturing overall system behaviour and, thirdly, the
uncertainties in the prediction and formulation of
appropriate overall economic system performance
objectives.
The parameterisation and the modelling
challenges require a staged approach for an overall
system optimisation. This ranges from simplified
system representations exposed to variations within
a large parameter space to more sophisticated
system models subject to evaluation for a reduced
and focused parameter zone. The description of the
system dynamics, operation and performance needs
to capture the key characteristics of the WEC
concept functionality, the technical implementation
and the economic application from the beginning
and throughout the optimisation and development
process.
The paper describes the problems that are
associated with the widely employed sequential
development of wave energy converter (WEC)
systems from concept through technology to
economic application and presents the methodology
applied to the overall techno-economic system
optimisation and development process of Wavebob
WECs
Techno-economic WEC system optimisation ā Methodology applied to Wavebob system definition
The overall system optimisation of wave energy
converters remains a challenging task. Firstly, this
is associated with the large number of system
parameters and their related constraints, secondly,
the complexity of numerical system representations
capturing overall system behaviour and, thirdly, the
uncertainties in the prediction and formulation of
appropriate overall economic system performance
objectives.
The parameterisation and the modelling
challenges require a staged approach for an overall
system optimisation. This ranges from simplified
system representations exposed to variations within
a large parameter space to more sophisticated
system models subject to evaluation for a reduced
and focused parameter zone. The description of the
system dynamics, operation and performance needs
to capture the key characteristics of the WEC
concept functionality, the technical implementation
and the economic application from the beginning
and throughout the optimisation and development
process.
The paper describes the problems that are
associated with the widely employed sequential
development of wave energy converter (WEC)
systems from concept through technology to
economic application and presents the methodology
applied to the overall techno-economic system
optimisation and development process of Wavebob
WECs
Prey capture by the cosmopolitan hydromedusae, Obelia spp., in the viscous regime
Author Posting. Ā© Association for the Sciences of Limnology and Oceanography, 2016. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 61 (2016): 2309ā2317, doi:10.1002/lno.10390.Obelia spp. are cnidarian hydromedusae with a cosmopolitan distribution but very little is known about their feeding. The small size of Obelia (bell diameter ā¼ 1 mm, tentacle width ā¼ 0.05 mm) suggests that feeding occurs in a viscous regime characterized by thick boundary layers. During feeding observations with a natural prey assemblage the majority of prey were captured at the tentacle tips during the contraction phase. Swimming kinematics from high speed videography confirmed that swimming was a low Re number process (Reā<ā50) and showed that maximum tentacle velocities occurred at the tentacle tips midway through a bell contraction. Flow visualizations from particle image velocimetry demonstrated that fluid motion between the tentacles was limited and that velocities were highest at the tentacle tips, leading to a thinning of boundary layer in this region. The highest nematocyst densities were observed in this same region of the tentacle tips. Taken together, the body kinematics, flow visualizations and nematocyst distributions of Obelia explain how these predators are able to shed viscous boundary layers to effectively capture microplanktonic prey. Our findings help explain how other small feeding-current medusae whose feeding interactions are governed by viscosity are able to successfully forage.National Science Foundation Grant Numbers: OCE- 1155084, DBI- 1455471, OCE- 1536672, OCE- 153668
Detailed computational procedure for design of cascade blades with prescribed velocity distributions in compressible potential flows
A detailed step-by-step computational outline is presented for the design of two-dimensional cascade blades having a prescribed velocity distribution on the blade in a potential flow of the usual compressible fluid. The outline is based on the assumption that the magnitude of the velocity in the flow of the usual compressible nonviscous fluid is proportional to the magnitude of the velocity in the flow of a compressible nonviscous fluid with linear pressure-volume relation
Maneuvering performance in the colonial siphonophore, Nanomia bijuga
Ā© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sutherland, K. R., Gemmell, B. J., Colin, S. P., & Costello, J. H. Maneuvering performance in the colonial siphonophore, Nanomia bijuga. Biomimetics, 4(3), (2019): 62, doi:10.3390/biomimetics4030062.The colonial cnidarian, Nanomia bijuga, is highly proficient at moving in three-dimensional space through forward swimming, reverse swimming and turning. We used high speed videography, particle tracking, and particle image velocimetry (PIV) with frame rates up to 6400 sā1 to study the kinematics and fluid mechanics of N. bijuga during turning and reversing. N. bijuga achieved turns with high maneuverability (mean lengthāspecific turning radius, R/L = 0.15 Ā± 0.10) and agility (mean angular velocity, Ļ = 104 Ā± 41 deg. sā1). The maximum angular velocity of N. bijuga, 215 deg. sā1, exceeded that of many vertebrates with more complex body forms and neurocircuitry. Through the combination of rapid nectophore contraction and velum modulation, N. bijuga generated high speed, narrow jets (maximum = 1063 Ā± 176 mm sā1; 295 nectophore lengths sā1) and thrust vectoring, which enabled high speed reverse swimming (maximum = 134 Ā± 28 mm sā1; 37 nectophore lengths sā1) that matched previously reported forward swimming speeds. A 1:1 ratio of forward to reverse swimming speed has not been recorded in other swimming organisms. Taken together, the colonial architecture, simple neurocircuitry, and tightly controlled pulsed jets by N. bijuga allow for a diverse repertoire of movements. Considering the further advantages of scalability and redundancy in colonies, N. bijuga is a model system for informing underwater propulsion and navigation of complex environments.This research was funded by the National Science Foundation (NSF) 1829932 and 173764 to K.R.S., NSF 1830015, 1536672, 1511721 to J.H.C., 1455440, 1536688, 1829913 to S.P.C., NSF 1511996 to B.J.G
The TREC2001 video track: information retrieval on digital video information
The development of techniques to support content-based access to archives of digital video information has recently started to receive much attention from the research community. During 2001, the annual TREC activity, which has been benchmarking the performance of information retrieval techniques on a range of media for 10 years, included a ātrackā or activity which allowed investigation into approaches to support searching through a video library. This paper is not intended to provide a comprehensive picture of the different approaches taken by the TREC2001 video track participants but instead we give an overview of the TREC video search task and a thumbnail sketch of the approaches taken by different groups. The reason for writing this paper is to highlight the message from the TREC video track that there are now a variety of approaches available for searching and browsing through digital video archives, that these approaches do work, are scalable to larger archives and can yield useful retrieval performance for users. This has important implications in making digital libraries of video information attainable
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